The present invention relates to improvements in cutter head assemblies intended for use in gear cutting operations. The cutter head assemblies are designed to carry cutting blades which have cutting face portions that are preserved during periodic resharpenings, and different types of cutting blades of this general character can be installed in cutter head assemblies of this invention to create single side, alternate side, or three-sided cutting actions with gear cutting machines capable of manufacturing spiral bevel and hypoid gears.
As discussed in U.S. Pat. No. 3,881,889 (commonly owned with the present application), it is known in this art to provide for cutter head assemblies which are designed to receive a plurality of cutting blades characterized by the ease with which they can be resharpened without disturbing a cutting (or front) face portion thereof. Cutting blades having this characterization offer advantages of ease of original manufacture from bar-stock and the possibility of metallurgical treatment of the critical cutting face portions of each blade. A type of cutter head assembly for receiving and carrying such blades is disclosed in U.S. Pat. No. 3,881,889 (and its companion Pat. No. 3,961,403), and the present invention represents an improvement in cutter head design when compared to the type of cutter head assembly shown in the aforesaid patent.
In addition, it is known in this art to provide for a cutter head assembly of the type shown in German Gebrauchsmuster No. 7,342,938 (registered for Werkzeugmaschinenfabrik Oerlikon-Buhrle A.G.) in which bar-stock cutting blades are carried in radially disposed and inclined (to the axis of rotation) slots in a cutter head assembly which thereby creates a relatively simple and easily assembled cutter head for gear cutting machines. However, the above-identified Gebrauchsmuster does not disclose a combination of cutting blade and cutter head geometry which permits the use of a variety of blade types with each blade having a front cutting face portion that can be preserved during resharpening thereof.
In accordance with the present invention a cutter head assembly includes certain basic components and features which are already known in the art. These features include the use of a cylindrical main body member having blade-receiving slots formed radially into its outer circumference and at an axial inclination to its center axis of rotation for receiving individual cutting blades, associated shims, and clamping blocks which position the blades in the blade-receiving slots. In addition, the assembly includes a ring member, as already known in the art, for enclosing the entire circumference of the main body member and for securing individual cutting blades within the blade-receiving slots. The individual cutting blades which are used in the cutter head assembly are characterized by their front face portions which do not require resharpening, as disclosed in the previously mentioned U.S. Pat. No. 3,881,889.
The improvements offered by the present invention for the type of cutter head assembly just described include specific features directed to the need for making such cutter head assemblies more universal in their capability for accepting different types of cutting blades for different gear cutting jobs. This need includes a requirement that a cutter head assembly can be set up to cut one, two, or three (inside, bottom, and outside) sides of a gear tooth slot for a given job and that such a cutter head assembly can be adjusted to different cutting diameters. This need is satisfied by specific design features of a cutter head assembly which includes the following combination of geometric and structural relationships:
1. Each blade-receiving slot is positioned to be generally included in or adjacent to a radius taken from the center axis of the main body member of the cutter head assembly so that a single blade carried within each slot can be radially adjusted relative to the center axis of the assembly. This feature provides for shimming of individual blades for purposes of truing a cutter or for adjusting its effective diameter. This adjustment can be made without changing the geometry requirements of cutting blades of the type contemplated herein.
2. Each blade-receiving slot is inclined to a plane passing through the center axis of rotation of the cutter head assembly at an included angle which is related to the pressure angle and side rake angle of any cutting blade to be received therein. This specific provision permits use of different cutting blade types as well as use of a range of pressure angles of up to 32.degree. and side rake angles of up to 25.degree. (for inside and outside cutting blades) for selected cutting blades, with no single blade having a negative hook angle in its mounted position relative to the cutter or workpiece. Slot inclinations for different pressure and rake angles can be determined in accordance with a formula which will be discussed later in this specification.
3. A plurality of cutting blades for use in the cutter head assembly with each of the cutting blades being of a type which includes a cutting face portion that is an extension of a shank portion thereof and which does not require resharpening when the cutting profile of the blade is resharpened. This feature permits the use of blades having treated or coated cutting faces. In addition, very specific cutting blade designs for inside and outside cutting blades are provided with built-in side rake angles in their shank cross-sections thereby permitting an easy change in side rake angle by simply selecting appropriate blade shank geometries.
The cutter head assembly of the present invention can be manufactured easily in accordance with known techniques, and additionally, it offers ease of assembly and disassembly when individual cutting blades are inserted and clamped (or conversely unclamped and removed) into (or out of) their respective slots. These and other features and advantages of the present invention will become apparent in the more detailed discussion which follows, and in that discussion reference will be made to the accompanying drawings as briefly described below.